This continuing project involves the adoption of the principle of Electro-Fluoro-Tomography to the transverse plane. These transverse tomograms are to be used for the purposes of localizing tumor, normal tissue structures and critical organs, and patient contour for the purpose of radiation therapy treatment planning. This information will then be transferred together with the therapists' input to the treatment planning computer. The transverse tomograms will be stored on a video disc for use in checking the therapy prescription, beam alignment, and patient set-up. Through the use of a large flat screen, low light level fluoroscope system, images (both transverse and normal) will be recorded on video disc and superimposed on the transverse section electronically. This will allow instant verification of treatment beam position with respect to both the treatment volumes and normal structures. BIBLIOGRAPHIC REFERENCES: Baily, N.A., Lasser, E.C., and Keller, R.A., Tumor Localization and Beam Monitoring--Electrofluorotomography. Medical Physics. (In Press).